Storage system providing automatic configuration updates for remote storage objects in a replication process

ABSTRACT

An apparatus is configured to generate a current snapshot set for a consistency group comprising a plurality of storage volumes subject to replication from a source storage system to a target storage system, to compare one or more configuration attributes of the current snapshot set to one or more configuration attributes of a previous snapshot set generated for the consistency group, to detect a change in at least one configuration attribute of the current snapshot set relative to the previous snapshot set based at least in part on the comparing, and to communicate the detected change in the configuration attribute from the source storage system to the target storage system so as to permit the target storage system to implement a corresponding configuration update for the consistency group. The generating, comparing, detecting and communicating are illustratively performed as part of an ongoing asynchronous or synchronous replication process carried out between the source and target storage systems.

FIELD

The field relates generally to information processing systems, and moreparticularly to storage in information processing systems.

BACKGROUND

Many information processing systems are configured to replicate datafrom one storage system to another storage system, possibly at differentphysical sites. In some cases, such arrangements are utilized to supportdisaster recovery functionality within the information processingsystem. For example, an enterprise may replicate data from a productiondata center to a disaster recovery data center. In the event of adisaster at the production site, applications can be started at thedisaster recovery site using the data that has been replicated to thatsite so that the enterprise can continue its business.

Data replication in these and other contexts can be implemented usingasynchronous replication at certain times and synchronous replication atother times. For example, asynchronous replication may be configured toperiodically transfer data in multiple cycles from a source site to atarget site, while synchronous replication may be configured to mirrorhost writes from the source site to the target site as the writes aremade at the source site. Storage systems participating in a replicationprocess can therefore each be configured to support both asynchronousand synchronous replication modes.

Conventional approaches to data replication can be problematic undercertain conditions. For example, it can be difficult to performconfiguration updates for storage volumes of a consistency group that issubject to an ongoing replication process involving source and targetstorage systems. More particularly, many conventional approaches requirean administrator or other user to perform manual resynchronization ofany such configuration updates between the source and target storagesystems. A manual resynchronization process of this type can be tediousand error prone. Similar problems arise with regard to configurationupdates for other types of remote storage objects during replication.

SUMMARY

Illustrative embodiments include one or more storage systems configuredto provide automatic configuration updates for remote storage volumes orother types of remote storage objects in a replication process. Forexample, some embodiments provide a fully automated approach in whichconfiguration changes are detected using current and previous snapshotsets at a source storage system and communicated from the source storagesystem to a target storage system. The target system automaticallyapplies the configuration changes from an active snapshot set maintainedat the target storage system to the consistency group at the targetstorage system. Such an arrangement allows a replication engine or othertype of replication control logic to precisely control the timing ofautomatic configuration updates at the target storage system, while alsocompletely eliminating any need for manual resynchronization. Thedisclosed techniques are applicable to storage volumes of a consistencygroup, as well as to other types of storage objects subject toreplication.

The source and target storage systems are illustratively implemented asrespective content addressable storage systems, although other types ofstorage systems can be used in other embodiments.

In one embodiment, an apparatus comprises at least one processing devicecomprising a processor coupled to a memory. The at least one processingdevice is configured to generate a current snapshot set for aconsistency group comprising a plurality of storage volumes subject toreplication from a source storage system to a target storage system, tocompare one or more configuration attributes of the current snapshot setto one or more configuration attributes of a previous snapshot setgenerated for the consistency group, to detect a change in at least oneconfiguration attribute of the current snapshot set relative to theprevious snapshot set based at least in part on the comparing, and tocommunicate the detected change in the configuration attribute from thesource storage system to the target storage system so as to permit thetarget storage system to implement a corresponding configuration updatefor the consistency group. The generating, comparing, detecting andcommunicating are illustratively performed as part of an ongoingasynchronous or synchronous replication process carried out between thesource and target storage systems.

The processing device in some embodiments is part of the source storagesystem, and more particularly implements at least a portion of a storagecontroller of the source storage system, although numerous alternativeimplementations are possible. For example, in other embodiments theprocessing device is implemented at least in part in a host deviceconfigured to communicate over a network with the source and targetstorage systems. As another example, the processing device can beimplemented in part in the source storage system and in part in thetarget storage system, possibly as a replication engine comprisingreplication control logic instances deployed in respective storagecontrollers of the source and target storage systems. Again, these areonly examples, and alternative implementations are possible.

A given one of the storage volumes illustratively comprises one or morelogical storage volumes each comprising at least a portion of a physicalstorage space of one or more storage devices. The term “storage volume”as used herein is therefore intended to be broadly construed, so as toencompass a set of one or more logical storage volumes.

In some embodiments, detecting a change in at least one configurationattribute of the current snapshot set relative to the previous snapshotset comprises detecting a change in a size of at least one of thestorage volumes.

Additionally or alternatively, detecting a change in at least oneconfiguration attribute of the current snapshot set relative to theprevious snapshot set illustratively comprises detecting a change in anidentity of at least one of the storage volumes.

Other types of configuration attributes and various combinations thereofcan be detected in other embodiments. The configuration attributes cancomprise configuration attributes for storage objects other than storagevolumes. For example, in some embodiments, the configuration attributesrelate to files, containers or other types of storage objects thatillustratively correspond to at least a portion of one or more storagevolumes of a consistency group.

In some embodiments, implementing a corresponding configuration updatefor the consistency group comprises updating an active snapshot set forthe consistency group in the target storage system to reflect the changein the configuration attribute. In such an arrangement, one or moresubsequent snapshot sets generated for the consistency group in thetarget storage system each automatically inherit the change in theconfiguration attribute. Implementing the corresponding configurationupdate for the consistency group may further comprise refreshing theconsistency group in the target storage system utilizing configurationattributes of the updated active snapshot set. The consistency group inthe target storage system is illustratively refreshed utilizing one ormore configuration attributes of the updated active snapshot set inconjunction with reassignment of the consistency group in the targetstorage system to a subsequent snapshot generated for the consistencygroup.

The source storage system in some embodiments comprises a clusteredimplementation of a content addressable storage system having adistributed storage controller. The content addressable storage systemin arrangements of this type is illustratively configured to utilizenon-volatile memory storage devices, such as flash-based storagedevices. For example, the storage devices of the source storage systemin such embodiments can be configured to collectively provide anall-flash storage array. The target storage system can similarlycomprise an all-flash storage array, or another type of contentaddressable storage system. Numerous other storage system arrangementsare possible in other embodiments. Content addressable storage istherefore not required.

These and other illustrative embodiments include, without limitation,apparatus, systems, methods and processor-readable storage media.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an information processing system comprisingsource and target storage systems configured to provide automaticconfiguration updates for remote storage objects in asynchronous orsynchronous replication in an illustrative embodiment.

FIG. 2 is a flow diagram of a process for providing automaticconfiguration updates for remote storage objects in asynchronous orsynchronous replication in an illustrative embodiment.

FIG. 3 shows an example of a snapshot tree utilized in conjunction withautomatic configuration updates for remote storage objects inasynchronous or synchronous replication in an illustrative embodiment.

FIG. 4 shows a content addressable storage system having a distributedstorage controller configured to provide automatic configuration updatesfor remote storage objects in asynchronous or synchronous replication inan illustrative embodiment.

FIGS. 5 and 6 show examples of processing platforms that may be utilizedto implement at least a portion of an information processing system inillustrative embodiments.

DETAILED DESCRIPTION

Illustrative embodiments will be described herein with reference toexemplary information processing systems and associated computers,servers, storage devices and other processing devices. It is to beappreciated, however, that these and other embodiments are notrestricted to the particular illustrative system and deviceconfigurations shown. Accordingly, the term “information processingsystem” as used herein is intended to be broadly construed, so as toencompass, for example, processing systems comprising cloud computingand storage systems, as well as other types of processing systemscomprising various combinations of physical and virtual processingresources. An information processing system may therefore comprise, forexample, at least one data center or other cloud-based system thatincludes one or more clouds hosting multiple tenants that share cloudresources. Numerous different types of enterprise computing and storagesystems are also encompassed by the term “information processing system”as that term is broadly used herein.

FIG. 1 shows an information processing system 100 configured inaccordance with an illustrative embodiment. The information processingsystem 100 comprises a plurality of host devices 101, a source storagesystem 102S and a target storage system 102T, all of which areconfigured to communicate with one another over a network 104. Thesource and target storage systems 102 are more particularly configuredin this embodiment to participate in an asynchronous or synchronousreplication process in which one or more storage volumes areasynchronously or synchronously replicated from the source storagesystem 102S to the target storage system 102T, possibly with involvementof at least one of the host devices 101. The one or more storage volumesthat are asynchronously or synchronously replicated from the sourcestorage system 102S to the target storage system 102T are illustrativelypart of a designated consistency group.

Each of the storage systems 102 is illustratively associated with acorresponding set of one or more of the host devices 101. The hostdevices 101 illustratively comprise servers or other types of computersof an enterprise computer system, cloud-based computer system or otherarrangement of multiple compute nodes associated with respective users.

The host devices 101 in some embodiments illustratively provide computeservices such as execution of one or more applications on behalf of eachof one or more users associated with respective ones of the hostdevices. Such applications illustratively generate input-output (IO)operations that are processed by a corresponding one of the storagesystems 102. The term “input-output” as used herein refers to at leastone of input and output. For example, TO operations may comprise writerequests and/or read requests directed to stored data of a given one ofthe storage systems 102.

The storage systems 102 illustratively comprise respective processingdevices of one or more processing platforms. For example, the storagesystems 102 can each comprise one or more processing devices each havinga processor and a memory, possibly implementing virtual machines and/orcontainers, although numerous other configurations are possible.

The storage systems 102 can additionally or alternatively be part ofcloud infrastructure such as an Amazon Web Services (AWS) system. Otherexamples of cloud-based systems that can be used to provide at leastportions of the storage systems 102 include Google Cloud Platform (GCP)and Microsoft Azure.

The storage systems 102 may be implemented on a common processingplatform, or on separate processing platforms.

The host devices 101 are illustratively configured to write data to andread data from the storage systems 102 in accordance with applicationsexecuting on those host devices for system users.

The term “user” herein is intended to be broadly construed so as toencompass numerous arrangements of human, hardware, software or firmwareentities, as well as combinations of such entities. Compute and/orstorage services may be provided for users under a Platform-as-a-Service(PaaS) model, an Infrastructure-as-a-Service (IaaS) model and/or aFunction-as-a-Service (FaaS) model, although it is to be appreciatedthat numerous other cloud infrastructure arrangements could be used.Also, illustrative embodiments can be implemented outside of the cloudinfrastructure context, as in the case of a stand-alone computing andstorage system implemented within a given enterprise.

The network 104 is assumed to comprise a portion of a global computernetwork such as the Internet, although other types of networks can bepart of the network 104, including a wide area network (WAN), a localarea network (LAN), a satellite network, a telephone or cable network, acellular network, a wireless network such as a WiFi or WiMAX network, orvarious portions or combinations of these and other types of networks.The network 104 in some embodiments therefore comprises combinations ofmultiple different types of networks each comprising processing devicesconfigured to communicate using Internet Protocol (IP) or othercommunication protocols.

As a more particular example, some embodiments may utilize one or morehigh-speed local networks in which associated processing devicescommunicate with one another utilizing Peripheral Component Interconnectexpress (PCIe) cards of those devices, and networking protocols such asInfiniBand, Gigabit Ethernet or Fibre Channel. Numerous alternativenetworking arrangements are possible in a given embodiment, as will beappreciated by those skilled in the art.

The source storage system 102S comprises a plurality of storage devices106S and an associated storage controller 108S. The storage devices 106Sstore storage volumes 110S. The storage volumes 110S illustrativelycomprise respective logical units (LUNs) or other types of logicalstorage volumes.

Similarly, the target storage system 102T comprises a plurality ofstorage devices 106T and an associated storage controller 108T. Thestorage devices 106T store storage volumes 110T, at least a portion ofwhich represent respective LUNs or other types of logical storagevolumes that are replicated from the source storage system 102S to thetarget storage system 102T in accordance with an asynchronous orsynchronous replication process.

The storage devices 106 of the storage systems 102 illustrativelycomprise solid state drives (SSDs). Such SSDs are implemented usingnon-volatile memory (NVM) devices such as flash memory. Other types ofNVM devices that can be used to implement at least a portion of thestorage devices 106 include non-volatile random access memory (NVRAM),phase-change RAM (PC-RAM) and magnetic RAM (MRAM). These and variouscombinations of multiple different types of NVM devices may also beused. For example, hard disk drives (HDDs) can be used in combinationwith or in place of SSDs or other types of NVM devices.

However, it is to be appreciated that other types of storage devices canbe used in other embodiments. For example, a given storage system as theterm is broadly used herein can include a combination of different typesof storage devices, as in the case of a multi-tier storage systemcomprising a flash-based fast tier and a disk-based capacity tier. Insuch an embodiment, each of the fast tier and the capacity tier of themulti-tier storage system comprises a plurality of storage devices withdifferent types of storage devices being used in different ones of thestorage tiers. For example, the fast tier may comprise flash drives orother types of SSDs while the capacity tier comprises HDDs. Theparticular storage devices used in a given storage tier may be varied inother embodiments, and multiple distinct storage device types may beused within a single storage tier. The term “storage device” as usedherein is intended to be broadly construed, so as to encompass, forexample, SSDs, HDDs, flash drives, hybrid drives or other types ofstorage devices.

In some embodiments, at least one of the storage systems 102illustratively comprises a scale-out all-flash content addressablestorage array such as an XtremIO™ storage array from Dell EMC ofHopkinton, Mass. Other types of storage arrays, including by way ofexample VNX® and Symmetrix VMAX® storage arrays also from Dell EMC, canbe used to implement storage systems 102 in other embodiments.

The term “storage system” as used herein is therefore intended to bebroadly construed, and should not be viewed as being limited to contentaddressable storage systems or flash-based storage systems. A givenstorage system as the term is broadly used herein can comprise, forexample, network-attached storage (NAS), storage area networks (SANs),direct-attached storage (DAS) and distributed DAS, as well ascombinations of these and other storage types, includingsoftware-defined storage.

Other particular types of storage products that can be used inimplementing storage systems 102 in illustrative embodiments includeall-flash and hybrid flash storage arrays such as Unity™software-defined storage products such as ScaleIO™ and ViPR®, cloudstorage products such as Elastic Cloud Storage (ECS), object-basedstorage products such as Atmos®, and scale-out NAS clusters comprisingIsilon® platform nodes and associated accelerators, all from Dell EMC.Combinations of multiple ones of these and other storage products canalso be used in implementing a given storage system in an illustrativeembodiment.

In some embodiments, communications between the host devices 101 and thestorage systems 102 comprise Small Computer System Interface (SCSI)commands. Other types of SCSI or non-SCSI commands may be used in otherembodiments, including commands that are part of a standard command set,or custom commands such as a “vendor unique command” or VU command thatis not part of a standard command set. The term “command” as used hereinis therefore intended to be broadly construed, so as to encompass, forexample, a composite command that comprises a combination of multipleindividual commands. Numerous other commands can be used in otherembodiments.

The storage controller 108S of source storage system 102S in the FIG. 1embodiment includes replication control logic 112S and a snapshotgenerator 114S.

Similarly, the storage controller 108T of target storage system 102Tincludes replication control logic 112T and a snapshot generator 114T.

Although not explicitly shown in the figure, additional components canbe included in the storage controllers 108, such as signature generatorsutilized in generating content-based signatures of data pages.

The instances of replication control logic 112S and 112T arecollectively referred to herein as replication control logic 112. Suchreplication control logic instances are also referred to herein asindividually or collectively comprising at least a portion of a“replication engine” of the system 100.

The replication control logic 112 of the storage systems 102 controlsperformance of the asynchronous or synchronous replication processcarried out between those storage systems, which as noted above in someembodiments further involves at least one of the host devices 101. Thedata replicated from the source storage system 102S to the targetstorage system 102T can include all of the data stored in the sourcestorage system 102S, or only certain designated subsets of the datastored in the source storage system 102S, such as particular designatedsets of LUNs or other logical storage volumes. Different replicationprocesses of different types can be implemented for different parts ofthe stored data. Also, the storage systems 102 can be configured tooperate in different replication modes of different types at differenttimes. For example, the storage systems 102 can transition from anasynchronous replication mode to a synchronous replication mode and viceversa.

A given storage volume designated for replication from the sourcestorage system 102S to the target storage system 102T illustrativelycomprises a set of one or more LUNs or other instances of the storagevolumes 110S of the source storage system 102S. Each such LUN or otherstorage volume illustratively comprises at least a portion of a physicalstorage space of one or more of the storage devices 106S. Thecorresponding replicated LUN or other storage volume of the storagevolumes 110T of the target storage system 102T illustratively comprisesat least a portion of a physical storage space of one or more of thestorage devices 106T.

The replication control logic 112 of the storage systems 102 in someembodiments is configured to control the performance of correspondingportions of an asynchronous or synchronous replication process of thetype illustrated in the flow diagram of FIG. 2. At least one of the hostdevices 101 in some embodiments can also include one or more instancesof replication control logic and possibly also one or more snapshotgenerators, as well as additional or alternative components such as asignature generator.

The storage controllers 108 of the storage systems 102 should also beunderstood to include additional modules and other components typicallyfound in conventional implementations of storage controllers and storagesystems, although such additional modules and other components areomitted from the figure for clarity and simplicity of illustration.

It will be assumed for the following description of the FIG. 1embodiment that there is an ongoing asynchronous or synchronousreplication process being carried out between the source storage system102S and the target storage system 102T in the system 100, utilizingtheir respective instances of replication control logic 112S and 112T.

The asynchronous replication process more particularly comprises acycle-based asynchronous replication process in which a consistencygroup comprising one or more storage volumes is replicated from thesource storage system 102S to the target storage system 102T over aplurality of asynchronous replication cycles. Such an arrangement isillustratively configured to guarantee data consistency between thestorage volumes of the consistency group on the source and theircorresponding replicated versions on the target.

The asynchronous replication is performed periodically over the multiplecycles. For example, a given one of the cycles utilizes differentialscanning of a current snapshot set relative to a previous snapshot setto generate differential data, also referred to as representing a“delta” between the two snapshot sets. The differential data or delta iscommunicated from the source storage system 102S to the target storagesystem 102T in a given replication cycle of the cycle-based asynchronousreplication process. The asynchronous replication is illustrativelyimplemented at least in part by or otherwise under the control of thesource and target instances of replication control logic 112S and 112T.

The synchronous replication process illustratively comprises synchronousreplication of the consistency group in which host writes to theconsistency group are mirrored from the source storage system 102S tothe target storage system 102T as the writes are made at the sourcestorage system 102S.

Some embodiments utilize only asynchronous replication, while othersutilize only synchronous replication, and still others utilize bothasynchronous and synchronous replication. Alternative replicationarrangements different than those of the illustrative embodiments hereincan be used in other embodiments.

The source storage system 102S generates a current snapshot set for aconsistency group comprising a plurality of storage volumes subject toreplication from the source storage system 102S to the target storagesystem 102T, and compares one or more configuration attributes of thecurrent snapshot set to one or more configuration attributes of aprevious snapshot set generated for the consistency group. The sourcestorage system 102S detects a change in at least one configurationattribute of the current snapshot set relative to the previous snapshotset based at least in part on the above-noted comparing of the currentand previous snapshot sets, and communicates the detected change in theconfiguration attribute to the target storage system 102T. Such anarrangement advantageously permits the target storage system 102T toimplement a corresponding configuration update for the consistencygroup, illustratively utilizing an active snapshot set maintained by thetarget storage system 102T, in a manner to be described in more detailbelow.

The operations of the source storage system 102S in generating thecurrent snapshot set for the consistency group, comparing one or moreconfiguration attributes of the current snapshot set to one or moreconfiguration attributes of the previous snapshot set, detecting changesin at least one configuration attribute based at least in part on thecomparing, and communicating the detected change to the target storagesystem 102T are illustratively performed as part of an ongoingreplication process carried out between the source storage system 102Sand the target storage system 102T.

Other types of comparisons can be used to detect configuration attributechanges in other embodiments. For example, changes can be detected bycomparing a snapshot set generated from a consistency group to aproduction version of the consistency group itself. The term “comparing”as used herein is therefore intended to be broadly construed, and shouldnot be viewed as being limited to certain particular types ofcomparisons used in some of the illustrative embodiments disclosedherein. Accordingly, in a given comparing operation as disclosed herein,all of the configuration attributes of a current snapshot set may becompared to all of the configuration attributes of a previous snapshotset, or just particular subsets of those configuration attributes may becompared, with the latter including in some cases only a singleconfiguration attribute of the current snapshot set being compared to asingle configuration attribute of the previous snapshot set. Numerousother comparison arrangements may be used, including arrangements inwhich configuration attributes of current and previous snapshot sets arecompared to determine if a particular configuration attribute isassociated with a given storage volume or other storage object in asnapshot of the current snapshot set but is not associated with acorresponding storage volume or other storage object in a snapshot ofthe previous snapshot set.

As noted above, the ongoing replication process illustratively comprisesasynchronous replication of the consistency group carried out over aplurality of asynchronous replication cycles, or synchronous replicationof the consistency group in which host writes to the consistency groupare mirrored from the source storage system 102S to the target storagesystem 102T as the writes are made at the source storage system 102S.

It is assumed for the present embodiment that there is a previoussnapshot set already available in the source storage system 102S. Forexample, the previous snapshot set may be available from a previouscycle of a cycle-based asynchronous replication process. In an initialasynchronous replication cycle, the entire content of the currentsnapshot set is illustratively transferred to from the source to thetarget, and differential scanning of the current snapshot set relativeto the previous snapshot set is not utilized. The current snapshot setfor the initial replication cycle becomes the previous snapshot set forthe next replication cycle. A previous snapshot set can similarly beavailable in the context of an ongoing synchronous replication process.

The current snapshot set and other snapshot sets referred to the contextof some embodiments herein are illustratively generated for aconsistency group that comprises multiple storage volumes. A snapshottree of the consistency group in such embodiments illustrativelycomprises multiple individual snapshot trees for respective ones of thestorage volumes, each generally having the same topology of nodes.Accordingly, generation of a snapshot set for a consistency groupillustratively comprises generating a plurality of snapshots forrespective ones of the multiple storage volumes. Such snapshot sets andassociated versions of the consistency group vary over time and arerepresented by nodes of the snapshot tree of the consistency group.Again, the snapshot tree for the consistency group may be viewed asillustratively comprising multiple superimposed snapshot trees for therespective storage volumes of the consistency group with each suchstorage volume snapshot tree having substantially the same topology asthe consistency group snapshot tree.

A given one of the snapshot trees corresponding to a particular one ofthe storage volumes more particularly comprises a root node, at leastone branch node, and a plurality of leaf nodes, with a given one of thebranch nodes representing a particular version of the storage volumefrom which a corresponding snapshot is taken. A first one of the leafnodes which is a child of the given branch node represents a subsequentversion of the storage volume, and a second one of the leaf nodes whichis a child of the given branch node comprises the corresponding snapshotproviding a point-in-time (PIT) copy of the particular version of thestorage volume.

An illustrative example of a consistency group snapshot tree of the typedescribed above is shown in FIG. 3, and will be described in greaterdetail below in conjunction with the flow diagram of FIG. 2.

In some embodiments, the snapshot trees comprise or are otherwiseassociated with additional information also arranged in the form of atree structure. For example, a given one of the snapshot trees may beassociated with one or more additional trees including at least one of a“dirty” tree that characterizes updates to logical addresses of thecorresponding storage volume, and a hash tree comprising content-basedsignatures of respective ones of the logical addresses of thecorresponding storage volume. All nodes of a given snapshot tree in someembodiments, including both branch nodes and leaf nodes, may each beassociated with corresponding metadata of both a dirty tree and a hashtree.

An instance of a differential scan in an asynchronous replicationprocess performed for the given snapshot tree in embodiments of thistype can further comprise aggregating information of at least one of thedirty tree and the hash tree between start and stop nodes of the givensnapshot tree.

A wide variety of other types of snapshot trees and possibly one or moreassociated additional trees can be used in other embodiments. Also, theterm “tree” as used herein is intended to be broadly construed so as tocomprise any type of data structure characterizing a plurality of nodesand a plurality of edges interconnecting respective pairs of the nodes.

The content-based signatures of the above-noted hash tree associatedwith a given storage volume in some embodiments comprise hash digests oftheir respective pages, each generated by application of a hash functionsuch as the well-known Secure Hashing Algorithm 1 (SHA1) to the contentof its corresponding page. Other types of secure hashing algorithms,such as SHA2 or SHA256, or more generally other hash functions, can beused in generating content-based signatures herein.

A given hash digest in illustrative embodiments is unique to theparticular content of the data page from which it is generated, suchthat two data pages with exactly the same content will have the samehash digest, while two pages with different content will have differenthash digests. It is also possible that other types of content-basedsignatures may be used, such as hash handles of the type describedelsewhere herein. A hash handle generally provides a shortenedrepresentation of its corresponding hash digest. More particularly, thehash handles are shorter in length than respective hash digests that aregenerated by applying a secure hashing algorithm to respective ones ofthe data pages. Hash handles are considered examples of “content-basedsignatures” as that term is broadly used herein.

In embodiments in which the storage systems 102 comprise contentaddressable storage systems, address metadata is illustratively utilizedto provide content addressable storage functionality within thosesystems. The address metadata in some embodiments comprises at least aportion of one or more logical layer mapping tables that map logicaladdresses of respective ones of the data pages of the storage volume tocorresponding content-based signatures of the respective data pages.Examples of logical layer mapping tables and other metadata structuresillustratively maintained by the storage controllers 108S and 108T ofrespective source and target storage systems 102S and 102T will bedescribed elsewhere herein.

The manner in which the source storage system 102S detects andcommunicates changes in configuration attributes in conjunction withasynchronous or synchronous replication of the consistency group willnow be described in further detail.

For example, detecting a change in at least one configuration attributeof the current snapshot set relative to the previous snapshot setcomprises detecting a change in a size of at least one of the storagevolumes.

As another example, detecting a change in at least one configurationattribute of the current snapshot set relative to the previous snapshotset comprises detecting a change in an identity of at least one of thestorage volumes, such as a SCSI identity or other type of identity of atleast one of the storage volumes.

Other examples of configuration attributes that are subject to automaticupdates in illustrative embodiments include user-defined tags, Qualityof Service (QoS) configurations, alert and/or notification thresholds,object names. These and other configuration attributes can includevarious types of storage metadata created or otherwise managed by hostdevices 101 and/or associated storage management applications. The term“configuration attribute” as used herein is therefore intended to bebroadly construed.

These and types of configuration attributes and various combinationsthereof can be detected in other embodiments. The configurationattributes can comprise configuration attributes for storage objectsother than storage volumes. For example, in some embodiments, theconfiguration attributes relate to files, containers or other types ofstorage objects that illustratively correspond to at least a portion ofone or more storage volumes of a consistency group. These and otherstorage objects can be subject to automatic configuration updates in themanner disclosed herein. A storage object in some embodiments comprisesa portion of a storage volume, and in other embodiments comprisesmultiple storage volumes. The automatic configuration update techniquesdisclosed herein can be adapted in a straightforward manner for use withthese and other types of storage objects.

In some embodiments, implementing a corresponding configuration updatefor the consistency group comprises updating an active snapshot set forthe consistency group in the target storage system 102T to reflect thechange in the configuration attribute. Such an arrangement isillustratively configured to ensure that one or more subsequent snapshotsets generated for the consistency group in the target storage system102T each automatically inherit the change in the configurationattribute.

For example, implementing a corresponding configuration update for theconsistency group further illustratively comprises refreshing theconsistency group in the target storage system 102T utilizingconfiguration attributes of the updated active snapshot set. Theconsistency group in the target storage system 102T is illustrativelyrefreshed utilizing one or more configuration attributes of the updatedactive snapshot set in conjunction with reassignment of the consistencygroup in the target storage system 102T to a subsequent snapshotgenerated for the consistency group.

Additional details regarding techniques for maintenance and utilizationof an active snapshot set in a target storage system can be found inU.S. patent application Ser. No. 16/253,793, filed Jan. 22, 2019 andentitled “Storage System with Data Consistency Checking in SynchronousReplication Using Active Snapshot Set,” which is incorporated byreference herein in its entirety.

As mentioned previously, the term “storage volume” as used herein isintended to be broadly construed, and should not be viewed as beinglimited to any particular format or configuration. The term “consistencygroup” as used herein is also intended to be broadly construed, and maycomprise one or more storage volumes.

A more particular example of the automatic configuration updatefunctionality described above will now be presented. In this example, itis assumed that the source and target storage systems 102 are configuredvia their respective instances of replication control logic 112 toprovide automatic configuration updates for storage volumes or otherstorage objects of a consistency group subject to an ongoing replicationprocess. More specifically, the replication control logic instances 112Sand 112T collectively implement automatic configuration updates forremote storage objects in asynchronous or synchronous replication of aconsistency group from the source to the target. The replication controllogic instances 112S and 112T collectively comprise a replication engineof the system 100.

The automatic configuration update process in the present exampleincludes the following steps:

1. In the case of asynchronous replication, the source storage system102S (“source”) periodically creates snapshot sets for respectivereplication cycles, and in the case of synchronous replication, thesource periodically creates snapshot sets for use in fast recovery. Inboth of these replication modes, in conjunction with creating a newsnapshot set, the source compares the configuration attributes of thenew snapshot set with the configuration attributes of the previoussnapshot set. Again, other types of comparisons, possibly involvingcomparisons of one or more snapshot sets and a production version of theconsistency group, can be used in other embodiments. For anyconfiguration attribute differences that are found, the source notifiesthe target storage system 102T (“target”) of the detected changes.

2. The target maintains an active snapshot set for the consistencygroup. In the case of asynchronous replication, the active snapshot setillustratively comprises a current snapshot set of the consistency groupin the target, and in the case of synchronous replication, the activesnapshot set illustratively comprises a special snapshot set created onthe target when enabling synchronous replication. The active snapshotset in both modes is used to generate subsequent snapshot sets for theconsistency group in the target. Upon receiving configuration attributechanges from source, the target updates the configuration attributes ofthe active snapshot set to reflect the specified changes, such thatsubsequent snapshot sets created from the active snapshot set in thetarget will each automatically inherit the configuration attributechanges.

3. The target periodically creates a new snapshot set and reassigns thetarget consistency group to that snapshot set. As this reassignmentupdates the data content of the target consistency group, it can onlyhappen when host devices are not actively accessing the consistencygroup storage volumes. It is therefore safe to update the configurationattribute changes for the consistency group in conjunction with thereassignment of the target consistency group to a new snapshot setderived from the active snapshot set.

4. Subsequent accesses by one or more of the host devices 101 to thereassigned target consistency group can include a SCSI discovery processso as to obtain the latest data and configuration attributes for thereassigned target consistency group.

The automatic configuration update process in this example ensures thatconfiguration attribute changes to remote storage objects of a targetconsistency group are applied at a particular time in an ongoingreplication process when host devices are guaranteed not to be accessingthose remote storage objects. The source in the context of thisparticular example can persist storage object configuration attributechanges with each snapshot set, and detect configuration changes bycomparing the configuration between snapshot sets, and/or between theproduction consistency group and a snapshot set. The target can updatethe configuration of its consistency group in conjunction withreassignment of the consistency group to a snapshot set that hasinherited the configuration attribute changes from the active snapshotset maintained by the target. Using snapshot sets on the source andtarget as a conduit, a replication engine can precisely control thetiming of automatic configuration updates. The active snapshot set ofthe target holds the configuration updates until it is safe to refreshthe target consistency group through the reassignment process. Sucharrangements advantageously avoid the tedious and error prone manualprocess that would otherwise be required to resynchronize configurationchanges on the replication source and target.

In the above example, the process steps are assumed to be performedprimarily by the source storage system 102S operating in cooperationwith the target storage system 102T via a replication engine comprisingtheir respective replication control logic instances 112S and 112T.Other arrangements of process steps can be used in other embodiments.Also, the particular ordering of the steps shown above can be varied.

The above-described illustrative embodiments include examples ofautomatic configuration updates for remote storage objects inasynchronous or synchronous replication. Such arrangementsadvantageously allow a wide variety of different configuration updatesto be made on remote storage objects in a particularly efficient mannerduring ongoing asynchronous or synchronous replication.

As indicated previously, these and other operations carried out inconjunction with a process providing automatic configuration updates forremote storage objects in asynchronous or synchronous replication areillustratively performed at least in part under the control of thereplication control logic 112.

Although illustrative embodiments are described in conjunction withparticular source and target consistency group snapshot arrangements, itis to be appreciated that a wide variety of other storage systemsutilizing flexible snapshot and reassignment technologies can be adaptedin a straightforward manner to incorporate automatic configurationupdate functionality as disclosed herein.

The storage systems 102 in the FIG. 1 embodiment are assumed to beimplemented using at least one processing platform each comprising oneor more processing devices each having a processor coupled to a memory.Such processing devices can illustratively include particulararrangements of compute, storage and network resources.

The storage systems 102 may be implemented on respective distinctprocessing platforms, although numerous other arrangements are possible.At least portions of their associated host devices may be implemented onthe same processing platforms as the storage systems 102 or on separateprocessing platforms.

The term “processing platform” as used herein is intended to be broadlyconstrued so as to encompass, by way of illustration and withoutlimitation, multiple sets of processing devices and associated storagesystems that are configured to communicate over one or more networks.For example, distributed implementations of the system 100 are possible,in which certain components of the system reside in one data center in afirst geographic location while other components of the system reside inone or more other data centers in one or more other geographic locationsthat are potentially remote from the first geographic location. Thus, itis possible in some implementations of the system 100 for the storagesystems 102 to reside in different data centers. Numerous otherdistributed implementations of the storage systems 102 and theirrespective associated sets of host devices are possible.

Additional examples of processing platforms utilized to implementstorage systems and possibly their associated host devices inillustrative embodiments will be described in more detail below inconjunction with FIGS. 5 and 6.

It is to be appreciated that these and other features of illustrativeembodiments are presented by way of example only, and should not beconstrued as limiting in any way.

Accordingly, different numbers, types and arrangements of systemcomponents such as host devices 101, storage systems 102, network 104,storage devices 106, storage controllers 108 and storage volumes 110 canbe used in other embodiments.

It should be understood that the particular sets of modules and othercomponents implemented in the system 100 as illustrated in FIG. 1 arepresented by way of example only. In other embodiments, only subsets ofthese components, or additional or alternative sets of components, maybe used, and such components may exhibit alternative functionality andconfigurations.

For example, in other embodiments, at least portions of theabove-described functionality for automatic configuration updates forremote storage objects in asynchronous or synchronous replication can beimplemented in one or more host devices, or partially in a host deviceand partially in a storage system. Illustrative embodiments are notlimited to arrangements in which all such functionality is implementedin source and target storage systems or a host device, and thereforeencompass various hybrid arrangements in which the functionality isdistributed over one or more storage systems and one or more associatedhost devices, each comprising one or more processing devices. Referencesherein to “one or more processing devices” configured to implementparticular operations or other functionality should be understood toencompass a wide variety of different arrangements involving one or moreprocessing devices of at least one storage system and/or at least onehost device.

As another example, it is possible in some embodiments that the sourcestorage system and the target storage system can comprise differentportions of the same storage system. In such an arrangement, areplication process is illustratively implemented to replicate data fromone portion of the storage system to another portion of the storagesystem. The terms “source storage system” and “target storage system” asused herein are therefore intended to be broadly construed so as toencompass such possibilities.

The operation of the information processing system 100 will now bedescribed in further detail with reference to the flow diagram of theillustrative embodiment of FIG. 2, which implements an asynchronous orsynchronous replication process with automatic configuration updates forremote storage objects. The steps of the process illustratively involveinteractions between a source storage system and a target storagesystem, referred to as respective “source” and “target” in thesefigures, illustratively utilizing replication control logic instancesand snapshot generators of storage controllers of the source and target.For example, replication control logic of the source interacts withreplication control logic of the target in performing an asynchronousreplication process or a synchronous replication process for aconsistency group. It is possible in other embodiments that at least oneof the storage systems does not include replication control logic and asnapshot generator, and in such embodiments these components are insteadimplemented in one or more host devices.

The process as illustrated in FIG. 2 includes steps 200 through 210, andis suitable for use in system 100 but is more generally applicable toother types of information processing systems in which data isreplicated from source to target. Also, the roles of source and targetcan be reversed, as in a situation in which a failover from source totarget occurs.

In step 200, the source generates a current snapshot set (“snap set”)for a consistency group (CG) comprising multiple storage volumes. Theconsistency group is subject to asynchronous or synchronous replicationfrom the source to the target. The term “snapshot set” as used herein isintended to be broadly construed, and in some embodiments a givensnapshot set can include only a single snapshot. Also, a consistencygroup in some embodiments can comprise only a single storage volume orother type of storage object.

In step 202, the source compares one or more configuration attributes ofthe current snap set to one or more configuration attributes of aprevious snapshot set generated for the consistency group.

In step 204, a determination is made as to whether or not any changeswere detected in one or more storage volume configuration attributes asa result of the comparison in step 202. If a change is detected in atleast one configuration attribute of the current snapshot set relativeto the previous snapshot set, the process moves to step 206, andotherwise the process moves to step 210 as indicated.

In step 206, the source communicates one or more detected changes to thetarget. Any of a wide variety of different messaging formats can be usedfor such communications. For example, the detected changes can becommunicated by including the corresponding information in one or moremessages that are ordinarily exchanged between the source and target aspart of the ongoing asynchronous or synchronous replication.Accordingly, some embodiments involve modifying an otherwiseconventional replication message from the source to the target toinclude configuration attribute changes detected by the source for oneor more storage objects that are part of a consistency group.

In step 208, the target updates its active snap set to reflect theconfiguration attribute changes previously detected and communicated bythe source. The target eventually refreshes the consistency group at thetarget using the active snap set, such that the refreshed consistencygroup at the target will automatically include any updates that weremade to the configuration attributes in the active snap set. The processthen moves to step 210.

In step 210, the ongoing replication process continues as indicated.This also involves the automatic configuration update process of FIG. 2returning to step 200 in order to generate another snap set for theconsistency group. That snap set becomes the current snapshot set, andthe prior snap set that it replaces becomes the previous snapshot set.

The FIG. 2 process continues as long as the consistency group is subjectto asynchronous or synchronous replication from the source to thetarget. Any configuration attribute changes that occur are detected bythe source and communicated to the target and will be automaticallyreflected in the target consistency group via the active snap setmaintained at the target in the manner described above.

FIG. 3 shows an example of a snapshot tree 300 for the consistency groupthat is subject to replication in the FIG. 2 process. It is assumed forthis example that the replication process is an asynchronous replicationprocess, although a similar snapshot tree configuration can be used in asynchronous replication process. Such a snapshot tree illustrativelyrepresents a combination of multiple superimposed snapshot trees forrespective ones of the storage volumes of the consistency group, witheach of the storage volume snapshot trees having substantially the sameformat as the snapshot tree 300. Thus, although the snapshot tree formatillustrated in the figure is for a consistency group, it is alsorepresentative of multiple individual snapshot trees for respectivestorage volumes of the consistency group.

The snapshot tree 300 comprises a root node and a plurality of branchnodes denoted CGn-2, CGn-1, CGn and CG. The root node represents aversion of the consistency group from which an initial PIT copy iscaptured as snapshot set S0. The branch nodes CGn-2, CGn-1 and CGnrepresent subsequent versions of the consistency group from whichrespective PIT copies are captured as subsequent snapshot sets Sn-2,Sn-1 and Sn, as the storage volumes of the consistency group change overtime responsive to execution of IO operations. The snapshot sets Sn-1and Sn are associated with respective previous and current asynchronousreplication cycles denoted as cycle n-1 and cycle n.

A given storage volume snapshot tree having a format of the type shownin FIG. 3 represents a storage volume and its snapshots over time. Eachleaf node represents a particular version of the storage volume or asnapshot of the storage volume, and each branch node represents a sharedancestor between a version of the storage volume, a snapshot of thestorage volume, or a child branch node. When a given snapshot of thestorage volume is created, two child leaf nodes are created, onerepresenting new updates to the storage volume after creation of thesnapshot, and the other representing the snapshot. The volume node fromwhich the snapshot was created therefore becomes a branch node in thesnapshot tree. When a given snap set of the consistency group is createdfor its member storage volumes, two new leaf nodes are created in eachof the snapshot trees of the respective storage volumes.

The snapshot set Sn in this example is a type of current snapshot set,and the snapshot set Sn-1 is a type of previous snapshot set. Aninstance of differential scanning performed as part of the asynchronousreplication process in this example utilizes as its start node thenon-root node corresponding to the previous snapshot set Sn-1 of theprevious replication cycle n-1 and utilizes as its stop node thenon-root node corresponding to the current snapshot set Sn of thecurrent replication cycle n. These start and stop nodes are associatedwith respective branch nodes CGn-1 and CGn. The branch nodes CGn-1 andCGn are representative of what are more generally referred to herein asrespective first and second nodes corresponding to respective previousand current snapshot sets.

The differential scan illustratively involves aggregating node metadatabetween the start and stop nodes, such as dirty tree and hash treemetadata. It is to be appreciated that terms such as “aggregating” and“aggregate” as used herein are intended to be broadly construed, and caninclude multiple different types of aggregation, such as aggregation ofdirty tree metadata followed by aggregation of hash tree metadata, witheach such aggregation type possibly proceeding in different directionsthrough at least portions of a given node chain and in some casesinvolving different node chains potentially having different sets ofnodes.

Terms such as “root node,” “non-root node,” “start node” and “stop node”as used herein are all intended to be broadly construed. A non-root nodeis considered to be any snapshot tree node that is not a root node.Start node and stop node designations for a given snapshot tree in someembodiments can be reversed relative to the designation arrangementsreferred to above in conjunction with the example of FIG. 3.Accordingly, such terms should not be construed as requiring aparticularly directionality for scanning the snapshot tree. It shouldalso be understood that a wide variety of other snapshot treearrangements may be used.

The FIG. 2 process is an example of one possible arrangement forproviding automatic configuration updates for remote storage objects inasynchronous or synchronous replication. Such an arrangement allows theremote storage objects to have their configuration attributes updated ina particular efficient manner and without the need for any type ofmanual resynchronization between the storage objects on the source andthe target.

The particular processing operations and other system functionalitydescribed in conjunction with the flow diagram of FIG. 2 are presentedby way of illustrative example only, and should not be construed aslimiting the scope of the disclosure in any way. Alternative embodimentscan use other types of processing operations to provide automaticconfiguration updates for remote storage objects in asynchronous orsynchronous replication. For example, the ordering of the process stepsmay be varied in other embodiments, or certain steps may be performed atleast in part concurrently with one another rather than serially. Also,one or more of the process steps may be repeated periodically, ormultiple instances of the process can be performed in parallel with oneanother in order to implement a plurality of different asynchronous orsynchronous replication processes for respective different consistencygroups comprising different sets of storage volumes or for differentstorage systems or portions thereof within a given informationprocessing system.

Functionality such as that described in conjunction with the flowdiagram of FIG. 2 can be implemented at least in part in the form of oneor more software programs stored in memory and executed by a processorof a processing device such as a computer or server. As will bedescribed below, a memory or other storage device having executableprogram code of one or more software programs embodied therein is anexample of what is more generally referred to herein as a“processor-readable storage medium.”

For example, storage controllers such as storage controllers 108 ofstorage systems 102 that are configured to control performance of one ormore steps of the FIG. 2 process in their corresponding system 100 canbe implemented as part of what is more generally referred to herein as aprocessing platform comprising one or more processing devices eachcomprising a processor coupled to a memory. A given such processingdevice may correspond to one or more virtual machines or other types ofvirtualization infrastructure such as Docker containers or Linuxcontainers (LXCs). The storage controllers 108, as well as other systemcomponents, may be implemented at least in part using processing devicesof such processing platforms. For example, in a distributedimplementation of a given one of the storage controllers 108, respectivedistributed modules of such a storage controller can be implemented inrespective containers running on respective ones of the processingdevices of a processing platform.

In some implementations of the FIG. 2 process, the source and targetstorage systems comprise content addressable storage systems configuredto maintain various metadata structures that are utilized in reading andwriting data pages within the systems. Examples of metadata structuresmaintained by the source and target storage systems in illustrativeembodiments include the logical layer and physical layer mapping tablesdescribed below. It is to be appreciated that these particular tablesare only examples, and other tables or metadata structures havingdifferent configurations of entries and fields can be used in otherembodiments.

An address-to-hash (“A2H”) utilized in some embodiments comprises aplurality of entries accessible utilizing logical addresses asrespective keys, with each such entry of the A2H table comprising acorresponding one of the logical addresses, a corresponding hash handle,and possibly one or more additional fields.

A hash-to-data (“H2D”) table utilized in some embodiments comprises aplurality of entries accessible utilizing hash handles as respectivekeys, with each such entry of the H2D table comprising a correspondingone of the hash handles, a physical offset of a corresponding one of thedata pages, and possibly one or more additional fields.

A hash metadata (“HMD”) table utilized in some embodiments comprises aplurality of entries accessible utilizing hash handles as respectivekeys. Each such entry of the HMD table comprises a corresponding one ofthe hash handles, a corresponding reference count and a correspondingphysical offset of one of the data pages. A given one of the referencecounts denotes the number of logical pages in the storage system thathave the same content as the corresponding data page and therefore pointto that same data page via their common hash digest. The HMD table mayalso include one or more additional fields.

A physical layer based (“PLB”) table utilized in some embodimentsillustratively comprises a plurality of entries accessible utilizingphysical offsets as respective keys, with each such entry of the PLBtable comprising a corresponding one of the physical offsets, acorresponding one of the hash digests, and possibly one or moreadditional fields.

As indicated above, the hash handles are generally shorter in lengththan the corresponding hash digests of the respective data pages, andeach illustratively provides a short representation of the correspondingfull hash digest. For example, in some embodiments, the full hashdigests are 20 bytes in length, and their respective corresponding hashhandles are illustratively only 4 or 6 bytes in length.

Also, it is to be appreciated that terms such as “table” and “entry” asused herein are intended to be broadly construed, and the particularexample table and entry arrangements described above can be varied inother embodiments. For example, additional or alternative arrangementsof entries can be used.

In some embodiments, the storage system comprises an XtremIO™ storagearray or other type of content addressable storage system suitablymodified to incorporate functionality for providing automaticconfiguration updates for remote storage objects in asynchronous orsynchronous replication as disclosed herein.

An illustrative embodiment of such a content addressable storage systemwill now be described with reference to FIG. 4. In this embodiment, acontent addressable storage system 405 comprises a plurality of storagedevices 406 and an associated storage controller 408. The contentaddressable storage system 405 may be viewed as a particularimplementation of a given one of the storage systems 102, andaccordingly is assumed to be coupled to the other one of the storagesystems 102 and to one or more host devices of a computer system withininformation processing system 100.

Although it is assumed that both the source storage system 102S and thetarget storage system 102T are content addressable storage systems insome embodiments, other types of storage systems can be used for one orboth of the source storage system 102S and the target storage system102T in other embodiments. For example, it is possible that at least oneof the storage systems 102 in an illustrative embodiment need not be acontent addressable storage system and need not include an ability togenerate content-based signatures. In such an embodiment, at leastportions of the automatic configuration update functionality of the oneor more storage systems can be implemented in a host device.

The storage controller 408 in the present embodiment is configured toimplement functionality for providing automatic configuration updatesfor remote storage objects in asynchronous or synchronous replication,of the type previously described in conjunction with FIGS. 1 through 3.For example, the content addressable storage system 405 illustrativelyparticipates as a source storage system in an asynchronous orsynchronous replication process with a target storage system that may beimplemented as another instance of the content addressable storagesystem 405.

The storage controller 408 includes distributed modules 412 and 414,which are configured to operate in a manner similar to that describedabove for respective corresponding replication control logic 112 andsnapshot generators 114 of the storage controllers 108 of system 100.Module 412 is more particularly referred to as distributed replicationcontrol logic, and illustratively comprises multiple replication controllogic instances on respective ones of a plurality of distinct nodes.Module 414 is more particularly referred to as a distributed snapshotgenerator, and illustratively comprises multiple snapshot generationinstances on respective ones of the distinct nodes.

The content addressable storage system 405 in the FIG. 4 embodiment isimplemented as at least a portion of a clustered storage system andincludes a plurality of storage nodes 415 each comprising acorresponding subset of the storage devices 406. Such storage nodes 415are examples of the “distinct nodes” referred to above, and otherclustered storage system arrangements comprising multiple storage nodesand possibly additional or alternative nodes can be used in otherembodiments. A given clustered storage system may therefore include notonly storage nodes 415 but also additional storage nodes, compute nodesor other types of nodes coupled to network 104. Alternatively, suchadditional storage nodes may be part of another clustered storage systemof the system 100. Each of the storage nodes 415 of the storage system405 is assumed to be implemented using at least one processing devicecomprising a processor coupled to a memory.

The storage controller 408 of the content addressable storage system 405is implemented in a distributed manner so as to comprise a plurality ofdistributed storage controller components implemented on respective onesof the storage nodes 415. The storage controller 408 is therefore anexample of what is more generally referred to herein as a “distributedstorage controller.” In subsequent description herein, the storagecontroller 408 is referred to as distributed storage controller 408.

Each of the storage nodes 415 in this embodiment further comprises a setof processing modules configured to communicate over one or morenetworks with corresponding sets of processing modules on other ones ofthe storage nodes 415. The sets of processing modules of the storagenodes 415 collectively comprise at least a portion of the distributedstorage controller 408 of the content addressable storage system 405.

The modules of the distributed storage controller 408 in the presentembodiment more particularly comprise different sets of processingmodules implemented on each of the storage nodes 415. The set ofprocessing modules of each of the storage nodes 415 comprises at least acontrol module 408C, a data module 408D and a routing module 408R. Thedistributed storage controller 408 further comprises one or moremanagement (“MGMT”) modules 408M. For example, only a single one of thestorage nodes 415 may include a management module 408M. It is alsopossible that management modules 408M may be implemented on each of atleast a subset of the storage nodes 415. A given set of processingmodules implemented on a particular one of the storage nodes 415therefore illustratively includes at least one control module 408C, atleast one data module 408D and at least one routing module 408R, andpossibly a management module 408M.

Communication links may be established between the various processingmodules of the distributed storage controller 408 using well-knowncommunication protocols such as IP, Transmission Control Protocol (TCP),and remote direct memory access (RDMA). For example, respective sets ofIP links used in data transfer and corresponding messaging could beassociated with respective different ones of the routing modules 408R.

Although shown as separate modules of the distributed storage controller408, the modules 412 and 414 in the present embodiment are assumed to bedistributed at least in part over at least a subset of the other modules408C, 408D, 408R and 408M of the storage controller 408. Accordingly, atleast portions of the automatic configuration update functionality ofthe modules 412 and 414 may be implemented in one or more of the othermodules of the storage controller 408. In other embodiments, the modules412 and 414 may be implemented as stand-alone modules of the storagecontroller 408.

The storage devices 406 are configured to store metadata pages 420 anduser data pages 422, and may also store additional information notexplicitly shown such as checkpoints and write journals. The metadatapages 420 and the user data pages 422 are illustratively stored inrespective designated metadata and user data areas of the storagedevices 406. Accordingly, metadata pages 420 and user data pages 422 maybe viewed as corresponding to respective designated metadata and userdata areas of the storage devices 406.

A given “page” as the term is broadly used herein should not be viewedas being limited to any particular range of fixed sizes. In someembodiments, a page size of 8 kilobytes (KB) is used, but this is by wayof example only and can be varied in other embodiments. For example,page sizes of 4 KB, 16 KB or other values can be used. Accordingly,illustrative embodiments can utilize any of a wide variety ofalternative paging arrangements for organizing the metadata pages 420and the user data pages 422.

The user data pages 422 are part of a plurality of LUNs configured tostore files, blocks, objects or other arrangements of data, each alsogenerally referred to herein as a “data item,” on behalf of users of thecontent addressable storage system 405. Each such LUN may compriseparticular ones of the above-noted pages of the user data area. The userdata stored in the user data pages 422 can include any type of user datathat may be utilized in the system 100. The term “user data” herein istherefore also intended to be broadly construed.

A given storage volume for which content-based signatures are generatedusing modules 412 and 414 illustratively comprises a set of one or moreLUNs, each including multiple ones of the user data pages 422 stored instorage devices 406.

The content addressable storage system 405 in the embodiment of FIG. 4is configured to generate hash metadata providing a mapping betweencontent-based digests of respective ones of the user data pages 422 andcorresponding physical locations of those pages in the user data area.Content-based digests generated using hash functions are also referredto herein as “hash digests.” Such hash digests or other types ofcontent-based digests are examples of what are more generally referredto herein as “content-based signatures” of the respective user datapages 422. The hash metadata generated by the content addressablestorage system 405 is illustratively stored as metadata pages 420 in themetadata area. The generation and storage of the hash metadata isassumed to be performed under the control of the storage controller 408.

Each of the metadata pages 420 characterizes a plurality of the userdata pages 422. For example, a given set of user data pages representinga portion of the user data pages 422 illustratively comprises aplurality of user data pages denoted User Data Page 1, User Data Page 2,. . . User Data Page n. Each of the user data pages in this example ischaracterized by a LUN identifier, an offset and a content-basedsignature. The content-based signature is generated as a hash functionof content of the corresponding user data page. Illustrative hashfunctions that may be used to generate the content-based signatureinclude the above-noted SHA1 secure hashing algorithm, or other securehashing algorithms known to those skilled in the art, including SHA2,SHA256 and many others. The content-based signature is utilized todetermine the location of the corresponding user data page within theuser data area of the storage devices 406.

Each of the metadata pages 420 in the present embodiment is assumed tohave a signature that is not content-based. For example, the metadatapage signatures may be generated using hash functions or other signaturegeneration algorithms that do not utilize content of the metadata pagesas input to the signature generation algorithm. Also, each of themetadata pages is assumed to characterize a different set of the userdata pages.

A given set of metadata pages representing a portion of the metadatapages 420 in an illustrative embodiment comprises metadata pages denotedMetadata Page 1, Metadata Page 2, . . . Metadata Page m, havingrespective signatures denoted Signature 1, Signature 2, . . . Signaturem. Each such metadata page characterizes a different set of n user datapages. For example, the characterizing information in each metadata pagecan include the LUN identifiers, offsets and content-based signaturesfor each of the n user data pages that are characterized by thatmetadata page. It is to be appreciated, however, that the user data andmetadata page configurations described above are examples only, andnumerous alternative user data and metadata page configurations can beused in other embodiments.

Ownership of a user data logical address space within the contentaddressable storage system 405 is illustratively distributed among thecontrol modules 408C.

The automatic configuration update functionality provided by modules 412and 414 in this embodiment is assumed to be distributed across multipledistributed processing modules, including at least a subset of theprocessing modules 408C, 408D, 408R and 408M of the distributed storagecontroller 408.

For example, the management module 408M of the storage controller 408may include a replication control logic instance that engagescorresponding replication control logic instances in all of the controlmodules 408C and routing modules 408R in order to implement anasynchronous or synchronous replication process.

In some embodiments, the content addressable storage system 405comprises an XtremIO™ storage array suitably modified to incorporateautomatic configuration update functionality as disclosed herein.

In arrangements of this type, the control modules 408C, data modules408D and routing modules 408R of the distributed storage controller 408illustratively comprise respective C-modules, D-modules and R-modules ofthe XtremIO™ storage array. The one or more management modules 408M ofthe distributed storage controller 408 in such arrangementsillustratively comprise a system-wide management module (“SYM module”)of the XtremIO™ storage array, although other types and arrangements ofsystem-wide management modules can be used in other embodiments.Accordingly, automatic configuration update functionality in someembodiments is implemented under the control of at least one system-widemanagement module of the distributed storage controller 408, utilizingthe C-modules, D-modules and R-modules of the XtremIO™ storage array.

In the above-described XtremIO™ storage array example, each user datapage has a fixed size such as 8KB and its content-based signature is a20-byte signature generated using the SHA1 secure hashing algorithm.Also, each page has a LUN identifier and an offset, and so ischaracterized by <lun_id, offset, signature>.

The content-based signature in the present example comprises acontent-based digest of the corresponding data page. Such acontent-based digest is more particularly referred to as a “hash digest”of the corresponding data page, as the content-based signature isillustratively generated by applying a hash function such as the SHA1secure hashing algorithm to the content of that data page. The full hashdigest of a given data page is given by the above-noted 20-bytesignature. The hash digest may be represented by a corresponding “hashhandle,” which in some cases may comprise a particular portion of thehash digest. The hash handle illustratively maps on a one-to-one basisto the corresponding full hash digest within a designated clusterboundary or other specified storage resource boundary of a given storagesystem. In arrangements of this type, the hash handle provides alightweight mechanism for uniquely identifying the corresponding fullhash digest and its associated data page within the specified storageresource boundary. The hash digest and hash handle are both consideredexamples of “content-based signatures” as that term is broadly usedherein.

Examples of techniques for generating and processing hash handles forrespective hash digests of respective data pages are disclosed in U.S.Pat. No. 9,208,162, entitled “Generating a Short Hash Handle,” and U.S.Pat. No. 9,286,003, entitled “Method and Apparatus for Creating a ShortHash Handle Highly Correlated with a Globally-Unique Hash Signature,”both of which are incorporated by reference herein.

As mentioned previously, storage controller components in an XtremIO™storage array illustratively include C-module, D-module and R-modulecomponents. For example, separate instances of such components can beassociated with each of a plurality of storage nodes in a clusteredstorage system implementation.

The distributed storage controller in this example is configured togroup consecutive pages into page groups, to arrange the page groupsinto slices, and to assign the slices to different ones of theC-modules. For example, if there are 1024 slices distributed evenlyacross the C-modules, and there are a total of 16 C-modules in a givenimplementation, each of the C-modules “owns” 1024/16=64 slices. In sucharrangements, different ones of the slices are assigned to differentones of the control modules 408C such that control of the slices withinthe storage controller 408 of the storage system 405 is substantiallyevenly distributed over the control modules 408C of the storagecontroller 408.

The D-module allows a user to locate a given user data page based on itssignature. Each metadata page also has a size of 8KB and includesmultiple instances of the <lun_id, offset, signature> for respectiveones of a plurality of the user data pages. Such metadata pages areillustratively generated by the C-module but are accessed using theD-module based on a metadata page signature.

The metadata page signature in this embodiment is a 20-byte signaturebut is not based on the content of the metadata page. Instead, themetadata page signature is generated based on an 8-byte metadata pageidentifier that is a function of the LUN identifier and offsetinformation of that metadata page.

If a user wants to read a user data page having a particular LUNidentifier and offset, the corresponding metadata page identifier isfirst determined, then the metadata page signature is computed for theidentified metadata page, and then the metadata page is read using thecomputed signature. In this embodiment, the metadata page signature ismore particularly computed using a signature generation algorithm thatgenerates the signature to include a hash of the 8-byte metadata pageidentifier, one or more ASCII codes for particular predeterminedcharacters, as well as possible additional fields. The last bit of themetadata page signature may always be set to a particular logic value soas to distinguish it from the user data page signature in which the lastbit may always be set to the opposite logic value.

The metadata page signature is used to retrieve the metadata page viathe D-module. This metadata page will include the <lun_id, offset,signature> for the user data page if the user page exists. The signatureof the user data page is then used to retrieve that user data page, alsovia the D-module.

Write requests processed in the content addressable storage system 405each illustratively comprise one or more IO operations directing that atleast one data item of the storage system 405 be written to in aparticular manner. A given write request is illustratively received inthe storage system 405 from a host device over a network. In someembodiments, a write request is received in the distributed storagecontroller 408 of the storage system 405, and directed from oneprocessing module to another processing module of the distributedstorage controller 408. For example, a received write request may bedirected from a routing module 408R of the distributed storagecontroller 408 to a particular control module 408C of the distributedstorage controller 408. Other arrangements for receiving and processingwrite requests from one or more host devices can be used.

The term “write request” as used herein is intended to be broadlyconstrued, so as to encompass one or more IO operations directing thatat least one data item of a storage system be written to in a particularmanner. A given write request is illustratively received in a storagesystem from a host device.

In the XtremIO™ context, the C-modules, D-modules and R-modules of thestorage nodes 415 communicate with one another over a high-speedinternal network such as an InfiniBand network. The C-modules, D-modulesand R-modules coordinate with one another to accomplish various IOprocessing tasks.

The write requests from the host devices identify particular data pagesto be written in the storage system 405 by their corresponding logicaladdresses each comprising a LUN ID and an offset.

As noted above, a given one of the content-based signaturesillustratively comprises a hash digest of the corresponding data page,with the hash digest being generated by applying a hash function to thecontent of that data page. The hash digest may be uniquely representedwithin a given storage resource boundary by a corresponding hash handle.

The content addressable storage system 405 utilizes a two-level mappingprocess to map logical block addresses to physical block addresses. Thefirst level of mapping uses an address-to-hash (“A2H”) table and thesecond level of mapping uses a hash metadata (“HMD”) table, with the A2Hand HMD tables corresponding to respective logical and physical layersof the content-based signature mapping within the content addressablestorage system 405. The HMD table or a given portion thereof in someembodiments disclosed herein is more particularly referred to as ahash-to-data (“H2D”) table.

The first level of mapping using the A2H table associates logicaladdresses of respective data pages with respective content-basedsignatures of those data pages. This is also referred to as logicallayer mapping.

The second level of mapping using the HMD table associates respectiveones of the content-based signatures with respective physical storagelocations in one or more of the storage devices 106. This is alsoreferred to as physical layer mapping.

Examples of these and other metadata structures utilized in illustrativeembodiments were described above in conjunction with FIG. 2. Theseparticular examples include respective A2H, H2D, HMD and PLB tables. Insome embodiments, the A2H and H2D tables are utilized primarily by thecontrol modules 408C, while the HMD and PLB tables are utilizedprimarily by the data modules 408D.

For a given write request, hash metadata comprising at least a subset ofthe above-noted tables is updated in conjunction with the processing ofthat write request.

The A2H, H2D, HMD and PLB tables described above are examples of whatare more generally referred to herein as “mapping tables” of respectivedistinct types. Other types and arrangements of mapping tables or othercontent-based signature mapping information may be used in otherembodiments.

Such mapping tables are still more generally referred to herein as“metadata structures” of the content addressable storage system 405. Itshould be noted that additional or alternative metadata structures canbe used in other embodiments. References herein to particular tables ofparticular types, such as A2H, H2D, HMD and PLB tables, and theirrespective configurations, should be considered non-limiting and arepresented by way of illustrative example only. Such metadata structurescan be implemented in numerous alternative configurations with differentarrangements of fields and entries in other embodiments.

The logical block addresses or LBAs of a logical layer of the storagesystem 405 correspond to respective physical blocks of a physical layerof the storage system 405. The user data pages of the logical layer areorganized by LBA and have reference via respective content-basedsignatures to particular physical blocks of the physical layer.

Each of the physical blocks has an associated reference count that ismaintained within the storage system 405. The reference count for agiven physical block indicates the number of logical blocks that pointto that same physical block.

In releasing logical address space in the storage system, adereferencing operation is generally executed for each of the LBAs beingreleased. More particularly, the reference count of the correspondingphysical block is decremented. A reference count of zero indicates thatthere are no longer any logical blocks that reference the correspondingphysical block, and so that physical block can be released.

It should also be understood that the particular arrangement of storagecontroller processing modules 408C, 408D, 408R and 408M as shown in theFIG. 4 embodiment is presented by way of example only. Numerousalternative arrangements of processing modules of a distributed storagecontroller may be used to implement automatic configuration updatefunctionality in a clustered storage system in other embodiments.

Additional examples of content addressable storage functionalityimplemented in some embodiments by control modules 408C, data modules408D, routing modules 408R and management module(s) 408M of distributedstorage controller 408 can be found in U.S. Pat. No. 9,104,326, entitled“Scalable Block Data Storage Using Content Addressing,” which isincorporated by reference herein. Alternative arrangements of these andother storage node processing modules of a distributed storagecontroller in a content addressable storage system can be used in otherembodiments.

Illustrative embodiments of a storage system with automaticconfiguration update functionality as disclosed herein can provide anumber of significant advantages relative to conventional arrangements.

For example, some embodiments provide a fully automated approach inwhich configuration changes are detected using current and previoussnapshot sets at a source storage system and communicated from thesource storage system to a target storage system. The target systemautomatically applies the configuration changes from an active snapshotset maintained at the target storage system to the consistency group atthe target storage system.

Such an arrangement allows a replication engine or other type ofreplication control logic to precisely control the timing of automaticconfiguration updates at the target storage system, while alsocompletely eliminating any need for manual resynchronization.

The disclosed techniques are applicable to storage volumes of aconsistency group, as well as to other types of storage objects,including by way of example files and containers, that are subject toreplication between source and target storage systems.

In some embodiments, the source and target storage systems areillustratively implemented as respective content addressable storagesystems, but in other embodiments one or more of the storage systems caninstead be a traditional storage array, which does not support any typeof content addressable storage functionality, with any missingfunctionality being provided by a host device.

Accordingly, functionality for automatic configuration updates forremote storage objects in asynchronous or synchronous replication asdisclosed herein can be implemented in a storage system, in a hostdevice, or partially in a storage system and partially in a host device.

It is to be appreciated that the particular advantages described aboveand elsewhere herein are associated with particular illustrativeembodiments and need not be present in other embodiments. Also, theparticular types of information processing system features andfunctionality as illustrated in the drawings and described above areexemplary only, and numerous other arrangements may be used in otherembodiments.

Illustrative embodiments of processing platforms utilized to implementhost devices and storage systems with automatic configuration updatefunctionality will now be described in greater detail with reference toFIGS. 5 and 6. Although described in the context of system 100, theseplatforms may also be used to implement at least portions of otherinformation processing systems in other embodiments.

FIG. 5 shows an example processing platform comprising cloudinfrastructure 500. The cloud infrastructure 500 comprises a combinationof physical and virtual processing resources that may be utilized toimplement at least a portion of the information processing system 100.The cloud infrastructure 500 comprises multiple virtual machines (VMs)and/or container sets 502-1, 502-2, . . . 502-L implemented usingvirtualization infrastructure 504. The virtualization infrastructure 504runs on physical infrastructure 505, and illustratively comprises one ormore hypervisors and/or operating system level virtualizationinfrastructure. The operating system level virtualization infrastructureillustratively comprises kernel control groups of a Linux operatingsystem or other type of operating system.

The cloud infrastructure 500 further comprises sets of applications510-1, 510-2, . . . 510-L running on respective ones of theVMs/container sets 502-1, 502-2, . . . 502-L under the control of thevirtualization infrastructure 504. The VMs/container sets 502 maycomprise respective VMs, respective sets of one or more containers, orrespective sets of one or more containers running in VMs.

In some implementations of the FIG. 5 embodiment, the VMs/container sets502 comprise respective VMs implemented using virtualizationinfrastructure 504 that comprises at least one hypervisor. Suchimplementations can provide automatic configuration update functionalityof the type described above for one or more processes running on a givenone of the VMs. For example, each of the VMs can implement replicationcontrol logic and/or snapshot generators for providing automaticconfiguration update functionality in the system 100.

An example of a hypervisor platform that may be used to implement ahypervisor within the virtualization infrastructure 504 is the VMware®vSphere® which may have an associated virtual infrastructure managementsystem such as the VMware® vCenter™. The underlying physical machinesmay comprise one or more distributed processing platforms that includeone or more storage systems.

In other implementations of the FIG. 5 embodiment, the VMs/containersets 502 comprise respective containers implemented using virtualizationinfrastructure 504 that provides operating system level virtualizationfunctionality, such as support for Docker containers running on baremetal hosts, or Docker containers running on VMs. The containers areillustratively implemented using respective kernel control groups of theoperating system. Such implementations can also provide automaticconfiguration update functionality of the type described above. Forexample, a container host device supporting multiple containers of oneor more container sets can implement one or more instances ofreplication control logic and/or snapshot generators for providingautomatic configuration update functionality in the system 100.

As is apparent from the above, one or more of the processing modules orother components of system 100 may each run on a computer, server,storage device or other processing platform element. A given suchelement may be viewed as an example of what is more generally referredto herein as a “processing device.” The cloud infrastructure 500 shownin FIG. 5 may represent at least a portion of one processing platform.Another example of such a processing platform is processing platform 600shown in FIG. 6.

The processing platform 600 in this embodiment comprises a portion ofsystem 100 and includes a plurality of processing devices, denoted602-1, 602-2, 602-3, . . . 602-K, which communicate with one anotherover a network 604.

The network 604 may comprise any type of network, including by way ofexample a global computer network such as the Internet, a WAN, a LAN, asatellite network, a telephone or cable network, a cellular network, awireless network such as a WiFi or WiMAX network, or various portions orcombinations of these and other types of networks.

The processing device 602-1 in the processing platform 600 comprises aprocessor 610 coupled to a memory 612.

The processor 610 may comprise a microprocessor, a microcontroller, anapplication-specific integrated circuit (ASIC), a field-programmablegate array (FPGA), graphics processing unit (GPU) or other type ofprocessing circuitry, as well as portions or combinations of suchcircuitry elements.

The memory 612 may comprise random access memory (RAM), read-only memory

(ROM), flash memory or other types of memory, in any combination. Thememory 612 and other memories disclosed herein should be viewed asillustrative examples of what are more generally referred to as“processor-readable storage media” storing executable program code ofone or more software programs.

Articles of manufacture comprising such processor-readable storage mediaare considered illustrative embodiments. A given such article ofmanufacture may comprise, for example, a storage array, a storage diskor an integrated circuit containing RAM, ROM, flash memory or otherelectronic memory, or any of a wide variety of other types of computerprogram products. The term “article of manufacture” as used hereinshould be understood to exclude transitory, propagating signals.Numerous other types of computer program products comprisingprocessor-readable storage media can be used.

Also included in the processing device 602-1 is network interfacecircuitry 614, which is used to interface the processing device with thenetwork 604 and other system components, and may comprise conventionaltransceivers.

The other processing devices 602 of the processing platform 600 areassumed to be configured in a manner similar to that shown forprocessing device 602-1 in the figure.

Again, the particular processing platform 600 shown in the figure ispresented by way of example only, and system 100 may include additionalor alternative processing platforms, as well as numerous distinctprocessing platforms in any combination, with each such platformcomprising one or more computers, servers, storage devices or otherprocessing devices.

For example, other processing platforms used to implement illustrativeembodiments can comprise converged infrastructure such as VxRail™,VxRack™, VxRack™ FLEX, VxBlock™, or Vblock® converged infrastructurefrom VCE, the Virtual Computing Environment Company, now the ConvergedPlatform and Solutions Division of Dell EMC.

It should therefore be understood that in other embodiments differentarrangements of additional or alternative elements may be used. At leasta subset of these elements may be collectively implemented on a commonprocessing platform, or each such element may be implemented on aseparate processing platform.

As indicated previously, components of an information processing systemas disclosed herein can be implemented at least in part in the form ofone or more software programs stored in memory and executed by aprocessor of a processing device. For example, at least portions of theautomatic configuration update functionality of one or more componentsof a storage system as disclosed herein are illustratively implementedin the form of software running on one or more processing devices.

It should again be emphasized that the above-described embodiments arepresented for purposes of illustration only. Many variations and otheralternative embodiments may be used. For example, the disclosedtechniques are applicable to a wide variety of other types ofinformation processing systems, host devices, storage systems, storagenodes, storage devices, storage controllers, asynchronous and/orsynchronous replication processes, snapshot generators and associatedcontrol logic and metadata structures. Also, the particularconfigurations of system and device elements and associated processingoperations illustratively shown in the drawings can be varied in otherembodiments. Moreover, the various assumptions made above in the courseof describing the illustrative embodiments should also be viewed asexemplary rather than as requirements or limitations of the disclosure.Numerous other alternative embodiments within the scope of the appendedclaims will be readily apparent to those skilled in the art.

What is claimed is:
 1. An apparatus comprising: at least one processingdevice comprising a processor coupled to a memory; said at least oneprocessing device being configured: to generate a current snapshot setfor a consistency group comprising a plurality of storage volumessubject to replication from a source storage system to a target storagesystem; to compare one or more configuration attributes of the currentsnapshot set to one or more configuration attributes of a previoussnapshot set generated for the consistency group; to detect a change inat least one configuration attribute of the current snapshot setrelative to the previous snapshot set based at least in part on thecomparing; and to communicate the detected change in the configurationattribute from the source storage system to the target storage system soas to permit the target storage system to implement a correspondingconfiguration update for the consistency group.
 2. The apparatus ofclaim 1 wherein said at least one processing device is implemented atleast in part within the source storage system.
 3. The apparatus ofclaim 2 wherein said at least one processing device comprises at least aportion of a storage controller of the source storage system.
 4. Theapparatus of claim 1 wherein the storage volumes comprise respectivelogical storage volumes each comprising at least a portion of a physicalstorage space of one or more storage devices.
 5. The apparatus of claim1 wherein detecting a change in at least one configuration attribute ofthe current snapshot set relative to the previous snapshot set comprisesdetecting a change in a size of at least one of the storage volumes. 6.The apparatus of claim 1 wherein detecting a change in at least oneconfiguration attribute of the current snapshot set relative to theprevious snapshot set comprises detecting a change in an identity of atleast one of the storage volumes.
 7. The apparatus of claim 6 whereindetecting a change in an identity of at least one of the storage volumescomprises detecting a change in a Small Computer System Interface (SCSI)identity of at least one of the storage volumes.
 8. The apparatus ofclaim 1 wherein the generating, comparing, detecting and communicatingare performed as part of an ongoing replication process carried outbetween the source storage system and the target storage system.
 9. Theapparatus of claim 8 wherein the ongoing replication process comprisesasynchronous replication of the consistency group carried out over aplurality of asynchronous replication cycles.
 10. The apparatus of claim8 wherein the ongoing replication process comprises synchronousreplication of the consistency group in which host writes to theconsistency group are mirrored from the source storage system to thetarget storage system as the writes are made at the source storagesystem.
 11. The apparatus of claim 1 wherein implementing acorresponding configuration update for the consistency group comprisesupdating an active snapshot set for the consistency group in the targetstorage system to reflect the change in the configuration attribute. 12.The apparatus of claim 11 wherein one or more subsequent snapshot setsgenerated for the consistency group in the target storage system eachautomatically inherit the change in the configuration attribute.
 13. Theapparatus of claim 11 wherein implementing a corresponding configurationupdate for the consistency group further comprises refreshing theconsistency group in the target storage system utilizing configurationattributes of the updated active snapshot set.
 14. The apparatus ofclaim 11 wherein the consistency group in the target storage system isrefreshed utilizing one or more configuration attributes of the updatedactive snapshot set in conjunction with reassignment of the consistencygroup in the target storage system to a subsequent snapshot generatedfor the consistency group.
 15. A method comprising: generating a currentsnapshot set for a consistency group comprising a plurality of storagevolumes subject to replication from a source storage system to a targetstorage system; comparing one or more configuration attributes of thecurrent snapshot set to one or more configuration attributes of aprevious snapshot set generated for the consistency group; detecting achange in at least one configuration attribute of the current snapshotset relative to the previous snapshot set based at least in part on thecomparing; and communicating the detected change in the configurationattribute from the source storage system to the target storage system soas to permit the target storage system to implement a correspondingconfiguration update for the consistency group; wherein the method isimplemented by at least one processing device comprising a processorcoupled to a memory.
 16. The method of claim 15 wherein the generating,comparing, detecting and communicating are performed as part of anongoing replication process carried out between the source storagesystem and the target storage system.
 17. The method of claim 15 whereinimplementing a corresponding configuration update for the consistencygroup comprises updating an active snapshot set for the consistencygroup in the target storage system to reflect the change in theconfiguration attribute.
 18. A computer program product comprising anon-transitory processor-readable storage medium having stored thereinprogram code of one or more software programs, wherein the program codewhen executed by at least one processing device causes said at least oneprocessing device: to generate a current snapshot set for a consistencygroup comprising a plurality of storage volumes subject to replicationfrom a source storage system to a target storage system; to compare oneor more configuration attributes of the current snapshot set to one ormore configuration attributes of a previous snapshot set generated forthe consistency group; to detect a change in at least one configurationattribute of the current snapshot set relative to the previous snapshotset based at least in part on the comparing; and to communicate thedetected change in the configuration attribute from the source storagesystem to the target storage system so as to permit the target storagesystem to implement a corresponding configuration update for theconsistency group.
 19. The computer program product of claim 18 whereinthe generating, comparing, detecting and communicating are performed aspart of an ongoing replication process carried out between the sourcestorage system and the target storage system.
 20. The computer programproduct of claim 18 wherein implementing a corresponding configurationupdate for the consistency group comprises updating an active snapshotset for the consistency group in the target storage system to reflectthe change in the configuration attribute.